1. Field of the Invention
The present invention relates to a steering torque detecting device used for a motor-driven power steering system installed in, for instance, an automobile.
2. Discussion of the Background
There has been known a steering torque detecting device of such a type that a steering shaft is divided into an input shaft and an output shaft, a torsion bar is provided between the input and output shafts to connect them, displacement caused by a twisting force in the torsion bar is converted into displacement in stroke by means of a displacement converting means constituted by gears provided between the input and output shafts, and the displacement in stroke is detected by a stroke type potentiometer.
There has been known another type of detecting device which is so constructed that such displacement in the torsion bar is converted into a rotational displacement by means of a displacement converting means constituted by gears, and the rotational displacement is detected by a rotation type potentiometer. Thus, a quantity of torque detected is used to rotate a motor for steering operation so as to correspond to the detected quantity.
Thus, in the conventional steering torque detecting device utilizing the displacement converting means formed of the gears to convert the displacement in torsion into the displacement in stroke or the displacement in rotation, there is a disadvantage in that the entire structure is complicated and is large-sized.